ath9k: use ieee80211_free_txskb

Using ieee80211_free_txskb for tx frames is required, since mac80211 clones
skbs for which socket tx status is requested.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Cc: stable@vger.kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index e2fe713..dd45edf 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -765,7 +765,7 @@
 
 	return;
 exit:
-	dev_kfree_skb_any(skb);
+	ieee80211_free_txskb(hw, skb);
 }
 
 static void ath9k_stop(struct ieee80211_hw *hw)